Electromagnetic protective device



Jan. 3, 1928.

' W. H. PETERSEN ELECTROMAGNETIC PROTECTIVE DEVICE Original Filed Dec. 11, 1925 7lzlehz 2 2272727 7 Feisty/n Patented Jan. 3, 1928.

UNITED STATES resistance.

RATENT FFIE.

WILHELM. HENNIN G PETERSEN, OF LUDVIKA, SVIEDEN, ASSIGNOR TO 'ALMANNA.

SVEIJSXA ELEKTRISKA AKTIEBOLAGET, VASTERAS, SW'EIDEN, A CORIGR-A- T101? OF SXVEDEN.

ELECTROMAGNETIC PROTECTIVE DEVICE.

Original application filed. December 11, 1925, Serial No. 74,706, and. in Sweden November 4, 1924.

Divided and this application filed July 21, 1926. Serial No. 123,867.

Relays ot' the kind which act to close a circuit through the release coil of a circuitbreaker for instance in the case of an overload, are often so arranged, that the source of current acting on the relay (for instance a L transmission system, it is likely to occur,

that on powerful short--circuit in the system, the current traversing the relay becomes too strong for being controlled by its own contacts. Forv such cases it has been proposed to use an intermediary relay which is energized by a shunt carrying only a portion of the'current, said shunt being closed for the releasing operation, while the main.

portion of the current normally traverses a- The latter may also serve as a blow-out coil for the contacts of the intermediary relay which normally short -circuits the releasing coil.

The present invention, which is a division of my application Serial No. 7 l,706, filed December 11, 1925, is based upon the lastmentioned principle and has for its object to utilize the ator -said parallel resistance in a still more ellicient degree. According to the invention, the resistance, which retains the shape of a coil, is so arranged that its ampere-turns also will act on the armature of the intermediary relay on the occasion of a release, while they in the same time may be utilized for blowing out the arc. In a preferred form of the invention, the intermediary relay is provided with a three-legged iron core on which the coil controlled by the primary relay is situated on one of the outer legs while the shunt coil is placed on the middle leg.

in the accompanying drawing, the aforesaid preferred form of the invention is illustrated. Fig. 1 shows a liagram of connections and Figs. 2 3 the mechanical design of an interm diary relay, adapted for nse onnection with the present invention, in two views perpendicular to one another.

Reierring to F 1, 1 is the primary and 2 the secondary winding of a current transformer. 3 a mechanically active conductor (her-e shown as a coil) and 4 the contacts of the primary relay. The primary relay may be of any appropriate type, for instance with or without time lag, and, in the former case, with a time lag dependent or not upon the amount of current or voltage. The current path from the secondary winding 2 is divided into two branches after passing through the coil 3, one of said branches passing directly through a coil 5 on the intermediary relay, while the other passes over the contacts 4 to another coil 6 of the said intermediary relay. The first coil (shunt coil) is placed on the middle leg, the second on one outer leg 01"- the three-legged iron core 7. Beyond these coils the two current paths ar united in one, but this is divided again, one branch passing through the release coil 8 of the circuit breaker and the other over the contacts 9 oi the intermediary relay, betore the current returns to the transformer.

Referring to Figs. 2 and 3, the armature 10 of the intermediary relay is pivoted in the middle leg of its iron core and provider with a spring 11 or the like which norially pulls it towards the non-wound outer leg, at stop 12 (preferably adjustable) normally preventing direct contact between the armature and the said outer leg. The contact 9 actuated by the armature is preferably not rigidly connected to the armature, but is pivoted thereto and actuated by means of a projection 13 movable to a certain extent independently of the armature, whereby the breaking will be more rapid. The contact 9 is provided with a special spring 14- pressing it against the corresponding fixed contact. A pair of shields 15, 16 embracing the contact point constitute a shunt of the magnetic field which acts to extinguish the arc.

The general manner of operation of the device is as follows: Normally the current flows only through the coil 3 of the primary relay and the coil 5 on the middle leg of the intermediary relay and back to the transformer over the contacts 9. Hereby a magnetic field is produced in the mtermediarv relay'whicli is divided between the two outer legs substantially in inverse proportion to" thewi'dth of the two, air gaps. Byrsuitably adjusting the stop 12 the attraction of the non-wound leg can be made to dominate a little over that of the leg carrying the coil 6. \Vhen the current'sinks to alow' value or to zero, the spring 11, which may be rather weak,-*keepstherelay stable in this position.

The spring 14-, on the contrary, may and should be of considerable strength for effecting a high contact pressure, which facilitates the I passage of large currents. When the current rises above'the permissible value coil 3 'causes its plunger to rise and close the circuit through the contacts 4-, thereby energizing the coil 6', which makes the attraction of the'magn'et legcarrying that coil predominant. As soon as the armature begins to tip overas a consequence hereof, the attrac 9 the release coil 8 is energized and the release effected.

I claim as my invention 1. In combinationjwith an electromagnetic device, a protective device including a circuit connectedto said electromagnetic device, two coils in said circuit, a second cir-r cuitadapted when closed to shunt one of sa-id'coils and adaptedto be closed by means controlled'by the other of said coils, a coil insaid second circuit, a core magnetically connecting the first-mentioned coil and the third mentioned coil, and a movable armature controlled by the magnetic flux in said core. I

2. In combination with an electroniagnetic device, a circuit:connected to saidelcctromagnetic device, a coil in said circuit, a second circuit adapted when'closed to'shunt said coil, a primary relay adapted to close said second circuit, said relay including a mechanically active conductor actuated by the current in said'first' mentioned 'circuit,a coil in said second circuit, a core by which the latter coil ismagnetically connected with said first mention'e'd coil, and an armature controlled by the flux in said core.

3. In combination with an electromagnetic device, a"circuit connected to said electromagnetic device" and including a primary relay, a. second circuit adapted wlien closed to shunt a port-ion of said first mentioned circuit and adapted to be closed by said primary relay, magnetically interconnected coils in saidfirst mentioned circuit and in said second circuit cooperating to form a secondary relay, and a movable armature actuated by said coils and adapted to open said'first mentioned circuit. 7

- 4; In combination with an electromagnetic device having an external circuit, a primary relay in said circuit, a coil in said circuit, a'

a second circuit adapted when closed to shuntsaid coil and adapted to be closed by sa-idrelay, a coil in said" second circuit, a core having three legs substantially in a common plane, the middle leg of said core forming the core of said first mentioned coil and oneof the other legs forming the core otthe'second mentioned coil, and an armature pivoted to said middle leg and adapted to open said'first mentioned circuit.

Intestimony-whereof I have signed my name tothis specification.

u iiainmii HENNING rnrnismz. 

